1. Field of the Invention
The present invention relates to a power factor correction circuit employing a DC/DC converter.
2. Description of the Related Art
Various kinds of consumer electronics devices such as TVs, refrigerators, etc., or otherwise electronic devices such as laptop computers, cellular phone terminals, and PDAs (Personal Digital Assistants), are each configured to operate receiving electric power from an external circuit, and to be capable of charging a built-in battery using electric power received from an external power supply. Such consumer electronics devices and electronic devices (which will collectively be referred to as “electronic devices” hereafter) each include a built-in power supply apparatus configured to perform AC/DC conversion of commercial AC voltage. Alternatively, such a power supply apparatus is configured as a built-in component included within an external power supply adapter (AC adapter) for such an electronic device.
The power supply apparatus includes a rectifier circuit (diode bridge circuit) configured to rectify an AC voltage, and an insulating DC/DC converter configured to step down the rectified voltage, and to supply the voltage thus stepped down to a load. AC/DC conversion by means of such a power supply apparatus involves the development of current pulses having a very high amplitude. Such current pulses lead to problems of increased radiation noise, increased network loss, and increased high-frequency components over the entire high-frequency region. In order to solve such problems, in a case in which a given electronic device requires not less than a certain amount of power consumption, there is a need to mount a PFC (power factor correction) circuit on such an electronic device. The PFC circuit is configured to monitor an AC input voltage and an input current, and to perform phase adjustment such that the phase of the AC input voltage and the phase of the input current match each other.